A known transmitarray unit cell of the state of the art, particularly from document WO 2012/085067, comprises:
a planar receive antenna, intended to receive an incident wave;
a planar transmit antenna intended to transmit the incident wave with a phase shift, and comprising first and second radiation surfaces separated from each other by a separation area to be electrically isolated, the transmit antenna and the receive antenna being electrically connected to each other;
a phase-shift circuit configured to introduce the phase shift, and comprising switches each having an on, respectively off, state, wherein the corresponding switch allows, respectively blocks, the flowing of a current between the first and second radiation surfaces of the transmit antenna;
a ground plane having the receive antenna and the transmit antenna arranged on either side thereof;
a first printed circuit board comprising a first surface provided with the receive antenna, and a second opposite surface provided with the ground plane,
a second printed circuit board comprising a first surface assembled on the ground plane by means of a bonding film, and a second opposite surface provided with the transmit antenna, where the first surface may be provided with switch biasing lines.
The phase-shift circuit of each unit cell enables to reconfigure the radiation diagram of the antenna comprising a transmitarray. The switches enable to modify the phase of the wave transmitted by each unit cell of the array. Such a transmitarray has many advantages:                the power efficiency at microwave frequencies and particularly at millimeter-range frequencies (in the order of a few GHz) due to the transmission in air between the radiation source(s) and the unit cells,        a decreased bulk, weight, and manufacturing cost due to the planar technology used (patch antennas on printed circuit boards),        a radiation diagram having a good polarization purity since imperfections may mutually compensate within the array,        a radiation diagram having a good quality in terms of shape of the beam and of the secondary lobes due to the position of the radiation source(s) located opposite the beam generated by the array.        
To obtain satisfactory performances, the characteristic dimension of unit cells should be smaller than or equal to the half-wavelength of the radiation source(s). When the spectral field of the radiation source(s) is, in particular, in the range from 30 GHz to 110 GHz, the corresponding wavelength is smaller than 1 cm. Now, the switches are formed at the second surface of the second printed circuit board, in the separation area. The forming of the switches thus becomes a problem due to the small dimensions of the transmit antenna. The switches, arranged inside of a package and placed on the second surface of the second printed circuit board, are then likely to significantly degrade the unit cell performances. Indeed, the package of each switch tends to disturb the close environment of the first and second radiation surfaces, and thereby affects the radiation diagram of the transmit antenna. Further, electric connections are present between the package and the transmit antenna to make the corresponding switch functional. Such electric connections make the switch integration more complex, by taking up a non-negligible space in the separation area, which has a small size.